Do not use the ring.h header installed on the system. Instead, import
the header into the QEMU codebase. This avoids problems when QEMU is
built against a Xen version too old to provide all the ring macros.
Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
CC: anthony.perard@citrix.com
CC: jgross@suse.com
In case the word size of the domU and qemu running the qdisk backend
differ BLKIF_OP_DISCARD will not work reliably, as the request
structure in the ring have different layouts for different word size.
Correct this by copying the request structure in case of different
word size element by element in the BLKIF_OP_DISCARD case, too.
Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Stefano Stabellini <sstabellini@kernel.org>
Signed-off-by: Stefano Stabellini <sstabellini@kernel.org>
Commit f9e98e5d7a ("xen/blkif: Avoid double access to
src->nr_segments") didn't go far enough: src->operation is also being
used twice. And nothing was done to prevent the compiler from using the
source side of the copy done by blk_get_request() (granted that's very
unlikely).
Move the barrier()s up, and add another one to blk_get_request().
Note that for completing XSA-155, the barrier() getting added to
blk_get_request() would suffice, and hence the changes to xen_blkif.h
are more like just cleanup. And since, as said, the unpatched code
getting compiled to something vulnerable is very unlikely (and not
observed in practice), this isn't being viewed as a new security issue.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Signed-off-by: Stefano Stabellini <sstabellini@kernel.org>
src is stored in shared memory and src->nr_segments is dereferenced
twice at the end of the function. If a compiler decides to compile this
into two separate memory accesses then the size limitation could be
bypassed.
Fix it by removing the double access to src->nr_segments.
This is part of XSA-155.
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Implement discard support for xen_disk. It makes use of the existing
discard code in qemu.
The discard support is enabled unconditionally. The tool stack may
provide a property "discard-enable" in the backend node to optionally
disable discard support. This is helpful in case the backing file was
intentionally created non-sparse to avoid fragmentation.
Signed-off-by: Olaf Hering <olaf@aepfle.de>
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
